Modular plugs are widely used to provide electrical connections between devices. For example, RJ-11 type modular plugs are typically found on telephone sets to connect the telephones to a modular jack which ultimately is connected to a telephone switch at the central office. Modular plugs and jacks are also used to connect together computer equipment. U.S. Pat. No. 5,419,720 shows the construction for a typical modular jack. Thus, a computer board may include a modular jack assembly providing a dozen or so jacks into which external devices can be plugged. For example, a communications module may have one or more such modular jack assemblies.
Computer connections, however, are susceptible to noise due to the high frequency signals which are transmitted along the cables between the computer and the external devices. Susceptibility to noise is a special concern in high density applications, such as in communication modules, where dozens of modular jacks must be provided for the connection of communication lines between the computer and a telephone switch. For example, commercial network providers to the INTERNET typically require hundreds of communications lines. Because of the noise that can be generated at the interface between the modular plug and the modular jack, the cross-talk between adjacent jacks can become significant in such applications. It is for this reason that modular jacks assemblies are constructed with shielding provided between the jacks within the assembly and encasing the entire housing of the assembly.
Referring to FIG. 1, a shielded modular jack assembly 20 is shown mounted on printed circuit board 60. The assembly 20 provides two rows of chambers 40 for receiving modular plugs (not shown). As will be shown, the exterior shielding 50 includes grounding pins which contact ground traces on the printed circuit board 60 to provide a path to ground when the assembly 20 is mounted to the board as shown.
FIG. 2 shows an exploded view of a prior art version of a shielded modular jack assembly 100 manufactured by AMP, Inc. The exterior shielding, composed of front and rear portions 102A and 102B, encases a housing 110 containing two rows of pin sub-assemblies 112, 114. Lower pin sub-assemblies 112 are inserted into a lower row of the housing 110, and upper pin sub-assemblies 114 are inserted into an upper row of the housing. Disposed between the two rows within the housing 110 is an interior shielding plate 104.
FIGS. 3-6 show more detailed views of the lower and upper contact pin sub-assemblies 112, 114 of the prior art. The lower contact pin sub-assembly 112 shown in FIGS. 3 and 4 is composed of a mounting plastic portion 120, a contacting plastic portion 121 and a set of contact pins 30 formed through each portion. Likewise, the sub-assembly 114 shown in FIGS. 5 and 6 is composed of mounting and contacting plastic portions 130, 131 and a set of contact pins 30. FIGS. 3 and 5 show the sub-assemblies in a pre-assembled condition. During manufacture, the sub-assemblies are bent into an L shape, as shown in FIGS. 4 and 6, by rotating the mounting portions 120, 130 about the centerline A--A in the direction indicated by the dotted lines in FIGS. 3 and 5. The pin sub-assemblies are assembled by inserting the contacting portions 121, 131 of the L-shaped sub-assemblies 112, 114 into the housing 110 as indicated in FIG. 2.
The housing 110 includes guides to facilitate the insertion of the upper and lower pin sub-assemblies. Referring again to FIGS. 3-6, the sub-assemblies 112, 114 include flanges 128, 138, locking wedges 127, 137 and outward notches 122, 132 which engage corresponding guides formed in the housing, as can be seen in the rear and side views of the housing depicted in FIG. 9. The rear of the housing includes flange guides 182 and wedge guides 181 into which the flanges 128, 138 and locking wedges 127, 137 are fitted, to guide the pin sub-assemblies into the housing. The side view shows that the wedge guides 181 have hook portions 183 which engage the locking wedges 127, 137 of the sub-assemblies to hold the sub-assemblies in place. The outward notches 122, 132 of the sub-assemblies fit into guide rails 140 formed in the housing. The guide rails 140 engage the notches 122, 132 to guide and retain the mounting portions 120, 130 of the sub-assemblies 112, 114 in position within the housing. In addition, each of the upper pin sub-assemblies 114 has a bump 133 formed on the notch 132 which acts as a snap fastener to hold the mounting portion 130 of the sub-assembly 114 in place.
The bending of the contact pin sub-assemblies 112, 114 during the manufacture of the modular jack assembly can be a source of defects in the final product because of the stress placed on the contact pins 30 upon bending. Moreover, where the manufacturing is performed manually, inconsistencies in handling by different assemblers are likely to result in variations in the quality of the final modular jack assemblies.
Referring again to FIG. 2, it can be seen that a portion of the contact pins 30 protrude from the mounting portions 120, 130 of each of the contact pin sub-assemblies 112, 114. When the pin sub-assemblies are inserted into the housing 110, all of the protruding pins are aligned along the bottom of the housing. The pins extend into a printed circuit board when the modular jack assembly is mounted onto the printed circuit board.
The pins protruding from the mounting portions 120, 130 of the pin sub-assemblies 112, 114 are aligned and held in position by virtue of the sub-assemblies being inserted into the housing 110 and by the rear portion of the external shielding 102B pressing against the sub-assemblies. Nevertheless, misalignment of the protruding pins among the sub-assemblies is possible, since each sub-assembly is assembled into the housing 110 separately from and is mechanically independent of the other sub-assemblies. A misalignment of the pins in the modular jack assembly can make it difficult to align the pins to the corresponding openings on the printed circuit board during assembly of the board.
It is an object of the present invention to provide a modular jack assembly that is less complex to manufacture, thus improving the reliability and quality of the final product. It is a further object of the present invention to provide a modular jack which is less complex with respect to mounting to printed circuit boards and which exhibits improved shielding from noise.